There are many different mallard based breeds, they are very diverse. Most require a regular pool of water. Muscovy are a bit different. They can breed with mallard based breeds but the offspring are sterile and called mules.
Muscovy are more mobile on ground, they roost like chickens, don't...
What breeds are you looking at? Mallard based or muscovy?
My main advice is to keep your drake to hen ratio at a good level. Drakes can harass and mate hens too much, so it's important to remove extras from the group.